Factor X Deficiency Due to a Compound Heterozygosis Between a New Mutation (Gla72Asp) in Exon 2 and an Already Known one (Gly154Arg) in Exon 5: Factor X Mar Del Plata1)

BACKGROUND

Investigation of rare bleeding disorders in Latin-America.

OBJECTIVES

The report of a new case of FX deficiency due to a compound heterozygosis.

METHODS

Accepted clotting procedures were used. Sequencing of DNA was carried out by means of Applied Biosystems Instruments.

RESULTS

A compound heterozygote due to the association of a new mutation (Gla72Asp) with an already known mutation (Gly154Arg) of the FX gene is reported. The proposita is a 38 year old female who had a moderate bleeding tendency (menorrhagia, epistaxis, easy bruising). The proposita has never received substitution therapy but in the occasion of a uterine biopsy. The mother was asymptomatic but was a heterozygote for the new mutation. The father was asymptomatic but had deserted the family and could not be investigated. After this abandonment the mother of the proposita re-married with an asymptomatic man and she gave birth to a son who was asymptomatic but was also heterozygous for the new mutation (Gla72Asp). As a consequence it has to be assumed that the first husband of the mother of the proposita was heterozygous for the known mutation (Gly154Arg).

CONCLUSIONS

This is the third case of a new mutation in the FX gene reported, during the past few years, in Argentina.

Neonatal onset of congenital factor X deficiency: a description of two novel mutations with 6-year follow-up

Factor X congenital deficiency is a rare coagulation disorder involving autosomal recessive transmission. The clinical situation depends on the extent of the defect and may appear at any age. We report a case of a term newborn who developed a life-threatening bleeding event on the first day of life because of a Factor X (FX) deficiency. Fresh frozen plasma and FX intravenous replacement therapy were administered with normalization of the coagulation test. Genetic analysis identified two novel mutations (c.517G>T; c.139delG) in heterozygous state in the proband that were confirmed in the parents. We also describe a 6-year follow-up during which the patient has been administered prophylactic replacement therapy. The description of these two novel mutations and the long clinical follow-up help to increase our knowledge of the genotype-phenotype correlation of congenital FX deficiency, and provide information on better ways of managing the replacement therapy in patients with similar mutations.

Unexplained Discrepancies in the Activity—Antigen Ratio in Congenital FX Deficiencies With Defects in the Catalytic Domain

Studies on molecular biology have considerably enhanced our understanding of congenital coagulation disorders but have failed so far to supply tools for an adequate classification of defects. In fact, mutations in the same domain may give rise to different phenotypes. Conversely, mutations in different domains, controlled by different exons, may cause similar patterns. The 37 kindreds with congenital factor X (FX) deficiency, known to have a defect in the catalytic domain, have been evaluated in an attempt to investigate the genotype—phenotype relation. Discrepant results were obtained because about half kindreds showed a type I pattern, namely a concomitant decrease in FX activity and antigen. The other half showed a type II pattern, namely a decrease in FX activity with a normal or near normal FX antigen. In a few instances, the allocation of the kindred either to type I or to type II defect could not be reached, due to the lack of information about the antigen.

The comparison of the kindreds in which the same mutation has been discovered by different investigations is not always possible also for lack of information.

The study analyzes the need to have a multipronged approach to the study of congenital FX deficiency. The indication of a mutation in a given domain does not provide clear information about the phenotype.